*Negative setup and Hold

[AmarMohan]

hello,
I need to know that what are all the changes that are observed in negative setup and hold analysis?
How is it different from positive setup and hold in terms of layout and simulation?
can u explain with diagram?

At what circumstances we use negative setup and hold?

 

[slutarius]

hello,
I need to know that what are all the changes that are observed in negative setup and hold analysis?

This is uncleared question. I can not get the idea.

hello,
How is it different from positive setup and hold in terms of layout and simulation?
can u explain with diagram?

For layout, i believe there is no difference between the negative/positive setup/hold. But you can see the difference in timing analysis of layout database.

For simulation, obviously this is a problem with negative timing. Library should inform in log file with a warning that Setup/Hold are violation, of-course this happen when you enable the coressponded feature in library and simulation environment. Beside, for some libraries, output value from the endpoint would be "X" which represented for unknow state of a signal which invoked in a timing violation endpoint.

At what circumstances we use negative setup and hold?

I have never used it.
Probably in IO paths, you can accept the negative timing once you make sure it is intentionally follow your expectation depending on the IO path specification.